In the manufacture of high-bulk tissue products, such as facial tissue, bath tissue, paper towels, and the like, it is common to use one or more throughdryers for partially drying the web or to bring the tissue web to a final dryness or near-final dryness. Generally speaking, throughdryers typically include a rotating cylinder having an upper deck that supports a drying fabric which, in turn, supports the web being dried. In one embodiment, heated air is provided by a hood above the drying cylinder and is passed through the web while the web is supported by the drying fabric. In an alternative embodiment, heated air is fed to the drying cylinder, passed through a web traveling around the drying cylinder, and is then fed to and collected in a hood.
When incorporated into a papermaking system, throughdryers offer many and various benefits and advantages. For example, throughdryers are capable of drying tissue webs without compressing the webs. Thus, moisture is removed from the webs, without the webs losing a substantial amount of bulk or caliper. In fact, throughdryers, in some applications, may even serve to increase the bulk of a web. Throughdryers are also known to contribute to various other important properties and characteristics of the webs.
The use of throughdryers, however, can be expensive. For instance, in addition to the capital costs associated with the equipment, throughdryers have relatively high-energy requirements. Therefore, a need currently exists for a system and process for reducing the energy costs associated with throughdryers, while still retaining all the benefits and advantages to using throughdryers.